<!DOCTYPE html>
<meta charset="UTF-8">
<style>
.target {
  width: 120px;
  height: 120px;
  display: inline-block;
  background-image: url(), url();
}
</style>
<body>
<script src="../interpolation/resources/interpolation-test.js"></script>
<script>
assertComposition({
  property: 'background-position',
  underlying: '40px 140px',
  addFrom: '60px 160px',
  addTo: '160px 260px',
}, [
  {at: -0.25, is: '75px 275px, 75px 275px'},
  {at: 0, is: '100px 300px, 100px 300px'},
  {at: 0.25, is: '125px 325px, 125px 325px'},
  {at: 0.5, is: '150px 350px, 150px 350px'},
  {at: 0.75, is: '175px 375px, 175px 375px'},
  {at: 1, is: '200px 400px, 200px 400px'},
  {at: 1.25, is: '225px 425px, 225px 425px'},
]);

assertComposition({
  property: 'background-position',
  underlying: 'top 20% left 40%',
  addFrom: 'left 60% top 80%',
  addTo: 'right 80% bottom 40%',
}, [
  {at: -0.25, is: '110% 105%, 110% 105%'},
  {at: 0, is: '100% 100%, 100% 100%'},
  {at: 0.25, is: '90% 95%, 90% 95%'},
  {at: 0.5, is: '80% 90%, 80% 90%'},
  {at: 0.75, is: '70% 85%, 70% 85%'},
  {at: 1, is: '60% 80%, 60% 80%'},
  {at: 1.25, is: '50% 75%, 50% 75%'},
]);

assertComposition({
  property: 'background-position',
  underlying: 'top 20% left 40%',
  addFrom: 'left 60% top 80%, top 180% left 160%',
  addTo: 'right 80% bottom 40%',
}, [
  {at: -0.25, is: '110% 105%, 235% 230%'},
  {at: 0, is: '100% 100%, 200% 200%'},
  {at: 0.25, is: '90% 95%, 165% 170%'},
  {at: 0.5, is: '80% 90%, 130% 140%'},
  {at: 0.75, is: '70% 85%, 95% 110%'},
  {at: 1, is: '60% 80%, 60% 80%'},
  {at: 1.25, is: '50% 75%, 25% 50%'},
]);

assertComposition({
  property: 'background-position',
  underlying: '40px 140px',
  replaceFrom: '100px 200px',
  addTo: '160px 260px',
}, [
  {at: -0.25, is: '75px 150px, 75px 150px'},
  {at: 0, is: '100px 200px, 100px 200px'},
  {at: 0.25, is: '125px 250px, 125px 250px'},
  {at: 0.5, is: '150px 300px, 150px 300px'},
  {at: 0.75, is: '175px 350px, 175px 350px'},
  {at: 1, is: '200px 400px, 200px 400px'},
  {at: 1.25, is: '225px 450px, 225px 450px'},
]);

assertComposition({
  property: 'background-position',
  underlying: '40px 140px',
  addFrom: '60px 160px',
  replaceTo: '200px 400px',
}, [
  {at: -0.25, is: '75px 275px, 75px 275px'},
  {at: 0, is: '100px 300px, 100px 300px'},
  {at: 0.25, is: '125px 325px, 125px 325px'},
  {at: 0.5, is: '150px 350px, 150px 350px'},
  {at: 0.75, is: '175px 375px, 175px 375px'},
  {at: 1, is: '200px 400px, 200px 400px'},
  {at: 1.25, is: '225px 425px, 225px 425px'},
]);
</script>
</body>
